The ICJ’s Jurisdiction in Chagos and the Role of the Advisory Opinion


On February 25, 2019, the International Court of Justice (“ICJ”) issued an Advisory Opinion (Legal Consequences of the Separation of the Chagos Archipelago from Mauritius in 1965) that concluded that the United Kingdom’s (“UK”) decolonization of Mauritius in the mid-1960s and its continued administration of the Chagos Archipelago to this day contravene international law. The ICJ’s Advisory Opinion has potent legal implications for states that were, and continue to be, colonizing powers. However, perhaps more interesting from an international law perspective, are the jurisdictional question that the case presents and the ICJ’s willingness to weigh in, through a non-binding advisory opinion, on an issue that has the flavor of a bilateral dispute.

The Advisory Opinion was delivered in response to a request from the United Nations General Assembly in June 2017. The United Nations (“UN”) has played a key role in decolonization since its inception in 1945, and particularly since 1960, when it issued the Declaration on the Granting of Independence to Colonial Countries and Peoples. According to Article 65 of the ICJ’s establishing statute, the Court “may give an advisory opinion on any legal question” at the request of a UN body, including and especially the UN General Assembly. Since Article 65 is permissive, the ICJ can, in its discretion, decline to issue an opinion; however, the ICJ has consistently maintained that only “compelling reasons” will lead it to refuse a request.

This case arises out of the UK’s colonization of Mauritius, which dates back to the beginning of the 19th century. After a century and a half of colonial rule, and at the peak of the post-World War II decolonization era, the UK began conversations with Mauritius to grant it independence. However, the same period was marked by discussions with the United States (“US”) regarding its desire to establish a military base on the Chagos Archipelago, part of the territory of Mauritius. The UK’s support for Mauritanian independence effectively became reliant upon severing the Chagos Archipelago from Mauritius and retaining it as the British Indian Ocean Territory. It was then leased to the US for use as a military base, which resulted in the forced removal of 1,500 to 2,000 Chagossians. The UK continues the administration of the Chagos Archipelago today and the US maintains an active military base on its biggest island, Diego Garcia.

The ICJ ultimately determined that the UK’s separation of Chagos from Mauritius had been unlawful, holding that “any detachment by the administering Power of part of a non-self-governing territory, unless based on the freely expressed and genuine will of the people of the territory concerned, is contrary to the right to self-determination.” As for the UK’s continued administration of the Chagos Archipelago, the ICJ determined that this too “constitutes a wrongful act,” and that “the United Kingdom is under an obligation to bring an end to its administration of the Chagos Archipelago as rapidly as possible.”

Given the UN Charter’s stated purpose of promoting self-determination, as well as the treaty and customary international law on the subject, the ICJ’s holding on the merits of the presented issue is unsurprising. Though the Advisory Opinion speaks volumes to the obligations of colonial states, more legally noteworthy is its decision to render an opinion at all. The arguments against hearing the issue are persuasive given that it deals with two states that have disputed the matter in the past; in 2001, Mauritius considered bringing its sovereignty claims against the UK at the ICJ in a contentious case, and in 2010, Mauritius brought an arbitration against the UK under the UN Convention on the Law of the Sea challenging its exercises of control over the Chagos Archipelago. The ICJ dismissed these concerns by emphasizing that the Advisory Opinion served to assist the UN General Assembly in its function of decolonizing territories, including such territories in Mauritius, which did not implicate the sovereignty dispute between the two countries.

Judge Donoghue, the ICJ’s American judge, issued the sole dissent, in which she agreed with the UK’s argument that the ICJ should have used its discretion to decline the request for an opinion. She stated that “[t]here are ‘compelling reasons’ to decline to give an advisory opinion when ‘to give a reply would have the effect of circumventing the principle that a State is not obliged to allow its disputes to be submitted to judicial settlement without its consent’” (quoting the ICJ’s advisory opinion in Western Sahara). Though the UK will “of course consider in detail” the Advisory Opinion, Alan Duncan, the British Minister of State for Europe and the Americas, has characterized the UN General Assembly’s request for an opinion as a “misuse of powers” and has maintained the UK’s position that the matter must be resolved bilaterally.

Though the Advisory Opinion is ostensibly a means for the UN General Assembly to better do its work, it is clear that it has legal ramifications for the UK. These ramifications will no doubt affect its relations, not only with Mauritius, but also with other territories it continues to occupy, such as Cyprus, which is also home to active military bases retained by the UK at the time of its independence. This case walks the line between opinion and judgment, and the actions taken by the UN and the UK in response will be informative regarding the legitimacy, efficacy, and wisdom of the ICJ in taking on similar issues in the future.